Rotating member and method for coating the same

ABSTRACT

A pulsed discharge is generated between tip ends of a rotating member such as a blade and a discharge electrode including a hard material such as cBN in dielectric liquid or gas by a power supply for discharge to melt the discharge electrode, and a part of the discharge electrode is attached to the tip end of the rotating member to form an abrasive coating film including the hard materials such as cBN.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to a rotating member such as a blade orlabyrinth seal for use in a gas turbine, steam turbine, compressor orthe like, and a method for coating the rotating-member. Moreparticularly, it relates to a rotating member on a part of which acoating film including a hard material is formed, and a method forcoating the rotating member.

2. Description of the Related Art

For a rotating member such as a blade or a labyrinth seal, a clearancebetween a rotating section and a stationary section such as a chipclearance between the blade and a casing or a shroud, or a sealclearance between the labyrinth seal and a honeycomb seal needs to bekept/set to be appropriate during operation of a gas turbine. When theclearance is set to be excessively large fearing for contact, anefficiency of the gas turbine drops. Conversely, when the clearance isset to be excessively small, a tip end of the rotating member breaks andcauses a trouble of the gas turbine.

Therefore, in consideration of the contact with surrounding members(casing, shroud, honeycomb seal, and the like) of the rotating member, atip end of a blade or a labyrinth seal is coated with an abrasivecoating of a relatively hard material for chipping off the material of acontact surface of the surrounding member. The surrounding member iscoated with an abradable coating of a material which is relativelyeasily chipped. Accordingly, the chip clearance or the seal clearance isadjusted to be minimized, when the side of the surrounding member ischipped off by the tip end of the rotating member by taking advantage ofa hardness difference of the coating at the time of driving of the gasturbine.

Here, FIG. 1A is a perspective view of a usual turbine blade, FIG. 1B isa perspective view of the turbine blade with a chip shroud, and FIG. 1Cis a perspective view of a compressor blade. It is to be noted that aplatform or a dovetail on a turbine disk side is omitted from thesefigures. In a turbine blade 1 shown in FIG. 1A, the whole surface of ablade tip end is coated with an abrasive coating 5a. In a turbine blade2 with a chip shroud shown in FIG. 1B, the whole surfaces of the tipends of chip fins 4 disposed on a chip shroud 3 (i.e., the tip ends ofthe turbine blade) are coated with abrasive coatings 5 b. Furthermore,for the blade 1 of the compressor shown in FIG. 1C, an abrasive coating5 c is applied over the region of the blade tip end (including thebackside of the figure).

Moreover, FIG. 2 is a sectional view showing one example of a labyrinthseal tip end. The labyrinth seal is disposed in the clearance between arotating section and a stationary section to prevent leakage of air orcombustion gas, and is a seal structure frequently used in a gas turbineand compressor. In general, an annular labyrinth seal 6 includingconcave/convex portion is disposed on a rotating section side, and ahoneycomb seal (not shown) including a structure easy to be chipped offis disposed on a stationary section side. FIG. 2 is a sectional view cutin a plane including a center axis of the labyrinth seal 6, and anabrasive coating 5d is applied to the tip end of the convex portion ofthe labyrinth seal 6.

These abrasive coatings have heretofore been applied by methods such aswelding, thermal spraying, and plating (e.g., see References 1 and 2).With the coating by the welding, a welding rod or a powder body is usedto coat predetermined portions such as the tip end of the turbine bladeor the labyrinth seal. With the coating by the thermal spraying,zirconia is thermally sprayed which has a small difference of thermalexpansion from a mother material and whose hardness is relatively high(Vickers hardness of 1300 HV). With the coating by the plating, abrasivegrains (Vickers hardness of 4500 HV) of cubic boron nitride (cBN) highin hardness is electrically attached by nickel plating.

It is to be noted that other prior arts related to the present inventionare described in References 3, 4.

[Reference 1]

Japanese Laid-Open Patent Publication No. 11-286768

[Reference 2]

Japanese Laid-Open Patent Publication No. 2000-345809

[Reference 3]

Japanese Laid-Open Patent Publication No. 7-301103

[Reference 4]

Japanese Laid-Open Patent Publication No. 8-319804

However, in the above-described methods, a portion which does not haveto be coated is masked in order to closely attach the abrasive coating,the surface to be coated needs to be blast-treated in order to enhanceadhesion, and there are problems that there are many pretreatments andcosts are high. In either conventional thermal spraying or platingmethod, there have been problems that the adhesion of the coating isbad, peel occurs at the time of the driving, an engine trouble iscaused, and additionally the chip clearance or the seal clearance is notkept to be appropriate. Furthermore, there has been a problem that withthe coating by the welding, only a metal much lower in hardness can becoated as compared with a ceramic, and therefore abrasive properties(properties for chipping off a material to be ground) are inferior.Moreover, there has been a problem that a quality level fluctuates by anoperator's expertise, and a welding crack easily occurs with respect toa material bad in thermal conductivity and small in elongation.Furthermore, there has been a problem that post-treatments such asgrinding for processing to a required dimension after the welding arerequired, and a lot of trouble is required.

Moreover, according to References 3 and 4, in the coating method,discharge is performed between the rotating member and an electrode onfirst discharge conditions such that the electrode is consumed, and theelectrode is formed in accordance with a shape of a coating film formingportion. Thereafter, the coating film is formed by discharge between theelectrode and the rotating member on second discharge conditions. Then,even when the electrode is not processed beforehand for a product shape,a coating object portion can appropriately be coated. On the firstdischarge conditions for consuming the electrode, the electrode is setto have a minus polarity, a pulse width is set to 1 μs or less, and acurrent value is set to 10 A or less. On the second discharge conditionsfor forming the coating film, the electrode is preferably set to havethe minus polarity, the pulse width is set to 2 to 10 μs, and thecurrent value is set to 5 to 20 A.

Moreover, in the conventional abrasive coating, since the whole area ofthe tip end of the blade is coated, there has been a problem that acoating range is broad and yield of products is bad.

Furthermore, heretofore, the coating has been performed by the platingor the thermal spraying. Therefore, in the production (manufacturing) ofthe labyrinth seal, coating pretreatments such as a blast process and aprocess of attaching a masking tape are required before the coating, andcoating post-treatments such as a process of removing the masking tapeare required after the coating. Therefore, an operation time requiredfor the production (manufacturing) of the labyrinth seal lengthens, andit is not easy to enhance productivity of the labyrinth seal.

Additionally, for the same reason, the abrasive coat cannot firmly beattached to the tip edge of a seal fin. Therefore, there has been aproblem that the abrasive coat easily peels off the tip edge of the sealfin and the quality level of the labyrinth seal is not stable.

SUMMARY OF THE INVENTION

The present invention has been developed to solve the above-describedvarious problems. That is, a first object of the present invention is toprovide a rotating member which does not require any pretreatment orpost-treatment and which has good adhesion and which is coated with aprecise and abrasive coating of a relatively hard material (hereinafterreferred to as a hard material in the present specification for the sakeof convenience) compared to a material of an opponent component thatcontacts with the rotating member during rotation, and a method forcoating the rotating member.

Moreover, the first object is also to provide a method for forming along-service-life coating in tests of high cycle fatigue (HCF) or lowcycle fatigue (LCF) in an abrasive coated component.

Furthermore, a second object of the present invention is to provide arotating member in which an area of coating of a hard material can beoptimized to enhance a yield and a method for coating the rotatingmember.

Additionally, a third object of the present invention is to provide arotating member in which an operation time required for production of alabyrinth seal is reduced and productivity of labyrinth components canbe enhanced and a method for coating the rotating member.

To achieve the first object, according to a first invention, there isprovided a method for coating a rotating member, comprising the stepsof: generating a pulsed discharge between a rotating member formed intoa predetermined shape and a discharge electrode of a green compact indielectric liquid or gas to transfer a hard material of the dischargeelectrode or a hard material changed from a material of the dischargeelectrode onto the rotating member by each discharge pulse so that ahard concavity and convexity is formed on the rotating member, whereinthe green compact includes the hard material or the material changinginto the hard material by the discharge; and repeatedly generating thedischarge pulse to form on the rotating member a hard coating filmhaving the concavity and convexity.

Moreover, according to a second invention, in the method for coating therotating member, the hard coating film is an abrasive coating film thatis formed on a part of the rotating member and rubs against and shavesan opponent component.

According to the first and second inventions, since the so-calleddischarge coating method is used, pretreatments such as masking andblast treatment or post-treatments such as the grinding are notnecessary, the coating film or a layer having good adhesion can beformed, further the coating film containing remarkably hard materialssuch as a cubic boron nitride (cBN) can be coated, and the hard coatingfilm and the coating film having good abrasive properties can be formed.

Abrasive properties are enhanced by the treatment on a condition for acoating having coarse surface.

Moreover, according to a third invention, the method comprises the stepsof: generating discharge between the rotating member and the dischargeelectrode on a first discharge condition on which the dischargeelectrode is consumed so that a shape of the discharge electrode is madeto conform to a shape of a coating film forming portion on the rotatingmember; and thereafter generating discharge between the dischargeelectrode and the rotating member on a second discharge condition toform the coating film on the rotating member.

Furthermore, according to a fourth invention, preferably, on the firstdischarge condition, the discharge electrode has a minus polarity, apulse width is 1 μs or less, and a current value is 10 A or less, and onthe second discharge condition, the discharge electrode has a minuspolarity, the pulse width is 2 to 10 μs, and a current value is 5 to 20A.

Additionally, the coating film is preferably formed on the tip end ofthe rotating member. Furthermore, for the hard member, as in an eighthinvention, the discharge electrode of a green compact containing one ofor a mixture of cBN, TiC, TiN, TiAlN, TiB₂, WC, Cr₃C₂, SiC, ZrC, VC,B₄C, Si₃N₄, ZrO₂—Y, and Al₂O₃.

Moreover, the material forming the hard member by the discharge ispreferably one of or a mixture of Ti, Cr, W, V, Zr, Si, Mo, and Nb or amixture of these, and these are formed into carbide by the discharge inan oil-to form a hard coating film.

Since a so-called discharge coating method is used according to thismethod, the tip end of the rotating member can easily be coated with thehard material. From the viewpoint of resistance to oxidation, a coatingfilm containing TiC, WC, or cBN is preferably formed on the rotatingmember that is driven at a low temperature, a coating film containingcBN or Cr₃C2 is used in the rotating member that is driven at a hightemperature, and a coating film containing ZrO₂—Y or Al₂O₃ is formed onthe rotating member that is driven at a further high temperature.

Accordingly, a fifth, sixth, seventh, and ninth invention, there isprovided a method of enhancing a fatigue strength of a coated surface.

A coating film which does not easily stretch as compared with a mothermaterial is formed on the surface. Then, since a thin coating film bearsa tensile load, the coating film on the surface easily cracks. In thecoating by a discharge surface treatment, since a hard layer is firmlywelded to the mother material, the crack of the coating film isdeveloped into that of the mother material. To avoid this, it isnecessary to form a coating film having a ductility, a layer forpreventing the development of the crack between the mother material andthe coating film, or a coating layer strong against pull.

In a fifth invention, in the coating film, a ratio of a coated areacoated with the hard material in a coating film forming portion, thatis, coverage is suppressed, a portion not coated with the hard material,that is, the portion having the ductility is scattered and left, and theductility is left.

In a sixth invention, the discharge electrode is made to contain a metalwhich does not easily form carbide, accordingly the portion of a metalhaving the ductility is scattered and formed between the hard materials,and the ductility is left.

In a seventh invention, a porous coating film mainly formed of a metalis formed as a base. Thereafter, since the coating film containing thehard material is formed on the porous coating film, the crack of thecoating layer is prevented from being developed into the mothermaterial.

In a ninth invention, the surface of the coating layer is peened, andresidual stress of compression is left. Even when the mother materialstretches, a tensile stress is reduced.

These fifth to seventh, and ninth inventions are effective not only forthe coating with the hard material but also for the discharge surfacetreatment for forming the coating film on the surface such aswear-resistant coating.

Moreover, according to the eighth invention, since a remarkably hardceramic usable in the coating of the hard material is provided, it ispossible to provide the coating of an effective hard material.

Furthermore, according to a tenth invention, there is provided arotating member having an abrasive coating film on a part thereof thatis formed by a pulsed discharge between the rotating member and adischarge electrode of a green compact in dielectric liquid or gas,wherein the green compact includes a hard material or a material thatchanges into a hard material by the discharge, and the abrasive coatingfilm includes the hard material of the green compact or the hardmaterial that is changed from the material of the green compact by thedischarge. The rotating member is characterized in that thepretreatments such as a masking or blast process or the post-treatmentssuch as grinding are not unnecessary and the coating film or the layerhaving good adhesion is formed. Furthermore, the coating film ispreferably formed on the tip end of the rotating member.

For the rotating member, the discharge is caused between the rotatingmember and the discharge electrode in the dielectric liquid or gas toform an abrasive coating film including the hard material on a part ofthe rotating member, so that the rotating member superior in abrasiveproperties can be formed.

According to the eleventh to fourteenth inventions, since the coatingfilm having the ductility is formed, the layer for preventing thedevelopment of the crack is formed between the mother material and thecoating film, and the coating layer strong against the pull is formed,the rotating member high in fatigue strength is provided.

Moreover, according to a fifteenth invention, a remarkably hard ceramicusable in the coating of the hard material is provided, and accordinglythe rotating member having good abrasive properties is provided.

To achieve the second object, according to a 16th invention, there isprovided a rotating member in which only the vicinity of a portion ofthe rotating member having a possibility of contact with a componentdisposed opposite to the rotating member is coated with a hard material.Accordingly, a rotating member little in labor of operation, small inelectrode use amount, good in yield of products and low in cost isobtained.

In a 17th invention, there is a further inexpensive rotating member inwhich a range to be coated is locally limited.

In an 18th invention, there is provided a rotating member coated in amethod for enhancing the abrasive properties of the tenth to 17thinventions. The rotating member is coated on the conditions for a coarsesurface roughness to enhance the abrasive properties.

A 19th invention is a concrete example of the 16th invention, and thereis provided a blade whose tip end is coated with a hard material. Only acorner of the blade in a rotation advance direction and the vicinity ofthe corner are coated with the hard material.

Since the range of the coating of the hard material is optimized, theyield can be enhanced, the operation time is shortened, and the coatingmaterial can be saved.

A 20th invention is a concrete example of the 17th invention, and thereis provided a rotating member in which the coating film is formed on notall, but some of blades of a rotor or a blisk. The number of coatedblades is minimized, and accordingly the operation time is reduced andthe coating material can further be saved.

To achieve a third object, in a 21st invention, the rotating member is arotating labyrinth seal component which is one of structure elements ofa labyrinth seal structure which suppresses leak of a gas or liquidbetween a stationary component and a rotating component.

The rotating member comprises an annular seal component main body, andan annular seal fin integrally formed on an outer peripheral surface ofthe seal component main body, and a tip edge of the seal fin is coatedwith a hard material. For the coat of the hard material, an electrodefor coating having consumability is used, a pulsed discharge is causedbetween the electrode for coating and the tip edge of the seal fin indielectric liquid or gas, and the coat includes the hard material formedof a constituting material of the electrode for coating formed on thetip edge of the seal fin by a discharge energy or a reactant of theconstituting material.

Here, in general, the “electrode for coating having the consumability”means a green compact electrode (including a thermally treated greencompact electrode) obtained by compression molding of a powdered metal(including a metal compound), a mixed material of the powdered metal anda powdered ceramic, or the powdered ceramic having conductivity.Further, “electrode for coating having the consumability” also means asilicon electrode formed of solid silicon. It is to be noted that theceramic having conductivity is appropriately subjected to a surfacetreatment.

According to a 21st invention, the coat of the hard material is acoating film including a hard material constituted of a constitutingmaterial of the electrode for coating or a reactant of the constitutingmaterial formed on the tip edge of the seal fin by a discharge energygenerated between the electrode for coating and the tip edge of the sealfin without performing plating or thermal spraying. Therefore, in theproduction of the rotating labyrinth seal component, coatingpretreatments such as a blast treatment and a process of attaching amasking tape and coating post-treatments such as a process of removingthe masking tape are unnecessary.

Moreover, since a boundary portion between the coat of the hard materialcoated by the discharge energy and a mother body of the seal fin hasalloy composition changing properties (alloy composition changesdepending on the position), the coat of the hard material can firmly beconnected to the tip edge of the seal fin.

Furthermore, in the 21st invention, preferably as in the 22nd invention,the coat of the hard material includes a plurality of local coatingfilms locally formed on a plurality of portions in a peripheraldirection in the tip edge of the seal fin.

By this constitution, the coat of the hard material includes a pluralityof local coats. Therefore, in other words, the coating film includingthe hard material constituted of the constituting material of theelectrode for coating or the reactant of the constituting material islocally formed on a plurality of portions of the peripheral direction inthe tip edge of the seal fin, not in the whole periphery of the tip edgeof the seal fin. Therefore, the electrode for coating can be formed in asmall and simple shape in accordance with the size or the shape of theportion to be treated in the tip edge of the seal fin. Moreover, theamount of an electrode material for use in the electrode for coating canbe reduced.

It is to be noted that as described above, since the coat of the hardmaterial (local coat of the hard material) can firmly be connected tothe tip edge of the seal fin, the entire rotating labyrinth sealcomponent can have sufficient abrasive properties by the local coat ofthe plurality of hard materials without coating the whole periphery ofthe tip edge of the seal fin with the hard material.

Further in the tenth invention, preferably as in the 15th invention, theelectrode for coating is the green compact electrode obtained bycompression molding of the powdered metal, the mixed material of thepowdered metal and the powdered ceramic, or the powdered ceramic havingthe conductivity, or the solid silicon electrode. Furthermore, theceramic is one of or a mixture of cBN, Cr₃C₂, TiC, TiN, TiAlN, TiB₂,ZrO₂—Y, ZrC, VC, B₄C, WC, SiC, Si₃N₄, and Al₂O₃.

Here, the “powdered metal” also includes a powdered metal compound. Itis to be noted that a ceramic that does not have conductivity isappropriately subjected to the surface treatment so as to secure theconductivity.

Moreover, in a 23rd invention, there is provided a labyrinth sealstructure which suppresses a leakage of a gas or liquid between astationary component and a rotating component, comprising: astationary-side seal component integrally disposed on the stationarycomponent; an annular seal component main body which is disposed insidethe stationary-side seal component and which is capable of rotatingintegrally with the rotating component and which is integrally disposedon the rotating component; an annular seal fin integrally formed on anouter peripheral surface of the seal component main body; and a hardcoat formed on the tip edge of the seal fin, wherein the hard coat is acoating film including a hard material constituted of a constitutingmaterial or a reactant of the constituting material of an electrode forcoating formed on the tip edge of the seal fin by a discharge energy ofa pulsed discharge between the electrode for coating and the tip edge ofthe seal fin, and the electrode for coating has consumability.

Here, the “stationary-side seal component” includes a honeycomb-shapedstationary honeycomb seal component, or a stationary abradable sealcomponent whose inside is coated with an abradable coat.

Moreover, in general, the “electrode for coating having theconsumability” means a green compact electrode (including a thermallytreated green compact electrode) obtained by compression molding of apowdered metal (including a metal compound), a mixed material of thepowdered metal and a powdered ceramic, or the powdered ceramic havingconductivity. Further, the “electrode for coating having theconsumability” also means a silicon electrode formed of solid silicon.It is to be noted that for the ceramic which does not have theconductivity, the surface of the ceramic powder which does not have theconductivity is subjected to a treatment for forming a conductivecoating film so as to appropriately secure the conductivity.

According to the 23rd invention, the rotating labyrinth seal componentincludes the coat of the hard material. Therefore, to integrally rotatethe rotating labyrinth seal component with the rotating component, evenwhen the stationary-side seal component is deformed, and the rotatinglabyrinth seal component contacts with the stationary-side sealcomponent, the stationary-side seal component is simply shaved by thecoat of the hard material in the rotating labyrinth seal component, andthe rotating labyrinth seal component is hardly shaved.

Accordingly, a clearance between the stationary-side seal and therotating labyrinth seal component is inhibited from being enlargedduring the rotation of the rotating component, and a seal effect of thelabyrinth seal structure can be kept in an appropriate state. Moreover,the rotating labyrinth seal component is set so as to slightly contactwith the stationary-side seal component during initial rotation of therotating component. Accordingly, during or after the initial rotation,the clearance between the stationary-side seal component and therotating labyrinth seal component can be reduced as much as possible,and the seal effect of the labyrinth seal structure can further beenhanced.

Moreover, the coat of the hard material is the coating film includingthe hard material constituted of the constituting material of theelectrode for coating or the reactant of the constituting materialformed on the tip edge of the seal fin by the discharge energy generatedbetween the electrode for coating and the tip edge of the seal finwithout performing the plating or thermal spraying. Therefore, in theproduction of the rotating labyrinth seal component, the coatingpretreatments such as the blast treatment and the process of attachingthe masking tape and the coating post-treatments such as the process ofremoving the masking tape are unnecessary.

Furthermore, since the boundary portion between the coat of the hardmaterial coated by the discharge energy and the mother material of theseal fin has alloy composition changing properties, the coat of the hardmaterial can firmly be connected to the tip edge of the seal fin.

Furthermore, in a 24th invention, preferably the coat of the hardmaterial includes a plurality of local coating films locally formed on aplurality of portions in the peripheral direction in the tip edge of theseal fin.

By this constitution, the coat of the hard material includes a pluralityof local coats of the hard material. Therefore, in other words, thecoating film including the hard material constituted of the constitutingmaterial of the electrode for coating or the reactant of theconstituting material is locally formed on a plurality of portions to betreated of the peripheral direction in the tip edge of the seal fin, notin the whole periphery of the tip edge of the seal fin. Therefore, theelectrode for coating can be formed into the small and simple shape inaccordance with the size or the shape of the portion to be treated inthe tip edge of the seal fin. Moreover, the amount of the electrodematerial for use in the electrode for coating can be reduced.

It is to be noted that as described above, since the coat of the hardmaterial (local coat of the hard material) can firmly be connected tothe tip edge of the seal fin, the entire rotating labyrinth sealcomponents can have sufficient abrasive properties by the local coats ofthe plurality of hard materials without coating-the whole periphery ofthe tip edge of the seal fin with the hard material.

In a 25th invention, there is provided a method for manufacturing arotating member of a blade or a labyrinth member, comprising: a firststep of forming a forging material or a casting material into apredetermined shape by mechanical processing; and a second step ofgenerating a pulsed discharge between a rotating member formed into apredetermined shape and a discharge electrode of a green compact orsolid silicon in dielectric liquid or gas to transfer a hard material ofthe discharge electrode or the hard material changed from a material ofthe discharge electrode onto the rotating member by each discharge pulseso that a hard concavity and convexity is formed on the rotating member,wherein the green compact includes the hard material or the materialchanging into the hard material by the discharge, and repeatedlygenerating the discharge pulse to form on the rotating member a hardcoating film having the concavity and convexity.

In a 26th invention, in the above-described manufacturing method, in thesecond step, an abrasive coating film that rubs against and shaves anopponent component is formed as the hard coating film on a part of therotating member.

In a 27th invention, there is provided the method for manufacturing therotating member, wherein the second step comprises the steps of forminga discharge electrode into a shape in accordance with a shape of apredetermined portion of the rotating member.

In a 28th invention, there is provided a method for providing dischargeconditions that the shape of the discharge electrode conform to that ofthe coating film forming portion of the rotating member to form theelectrode without any trouble.

In a 29th invention, there is provided the method for manufacturing therotating member which does not easily collapse from fatigue, whereinduring the forming of the coating film in the second step, a dischargecondition is controlled to set a coverage to be 95% or less in thecoating film forming portion, the coverage being a ratio of an area atwhich the coating film including the hard material is formed.

In a 30th invention, there is provided the method of manufacturing therotating member, wherein the ratio of the coverage is controlled toprovide the rotating member which does not easily collapse from fatigue.

In a 31st invention, there is provided the method for manufacturing therotating member which does not easily collapse from fatigue, wherein inthe second step, the green compact electrode containing 5% or more byvolume of a metal which does not easily react into carbide is used toperform the discharge.

In a 32nd invention, there is provided the method for manufacturing therotating member which does not easily collapse from fatigue, wherein thesecond step comprises the steps of: forming a porous coating film on acoating film forming portion of the rotating member; and thereafterforming the coating film including the hard material on the porouscoating film. In a 33rd invention, there is provided the method formanufacturing the rotating member superior in abrasive properties byusing the appropriate discharge electrode material of the green compactin the second step.

In a 34th invention, there is provided the method of manufacturing therotating member which does not easily collapse from fatigue, furthercomprising: a third step of subjecting the coating film formed in thesecond step to a peening treatment.

Other objects and advantageous characteristics of the present inventionwill be apparent from the following description with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of a usual turbine blade, FIG. 1B is aperspective view of the turbine blade with a chip shroud, and FIG. 1C isa perspective view of a compressor blade;

FIG. 2 is a perspective view showing one example of a conventionallabyrinth seal tip end;

FIG. 3 is a diagram showing a first embodiment of a rotating member andcoating method of the present invention;

FIG. 4 is a diagram showing a second embodiment of the rotating memberand coating method of the present invention;

FIG. 5 is a diagram showing a third embodiment of the rotating memberand coating method of the present invention;

FIG. 6 is a diagram showing a fourth embodiment of the rotating memberand coating method of the present invention;

FIGS. 7A, 7B, and 7C are perspective views of the usual turbine bladeaccording to a fifth embodiment of the rotating member of the presentinvention;

FIGS. 8A, 8B, and 8C are perspective views of the turbine blade with achip shroud according to a sixth embodiment of the rotating member ofthe present invention;

FIGS. 9A, and 9B are perspective views of the compressor blade accordingto a seventh embodiment of the rotating member of the present invention;

FIG. 10 is a diagram showing the fifth embodiment of the coating methodaccording to the present invention;

FIG. 11 is a schematic diagram of a labyrinth seal structure accordingto an eighth embodiment of the rotating member of the present invention;

FIG. 12 is a front view of a labyrinth seal of FIG. 11; and

FIG. 13 is a schematic diagram of a discharge processing machineaccording to the eighth embodiment of the coating method according-tothe present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Preferable embodiments of the present invention will hereinafter bedescribed with reference to the drawings. It is to be noted thatcomponents common to the respective drawings are denoted with the samereference numerals, and redundant description is omitted.

FIG. 3 is a diagram showing a first embodiment of a rotating member andcoating method of the present invention. This figure shows that a tipend of a blade 1 for use in a gas turbine or a compressor is coated witha hard material.

In the method of the present invention, as shown in FIG. 3, the blade 1and a discharge electrode 11 including cubic boron nitride (cBN) issubmerged in a processing tank 12 filled with dielectric liquid (oil). Apulsed discharge is caused between the tip end of the blade 1 and thedischarge electrode 11 by a power supply for discharge 14 to melt thedischarge electrode 11. A part of the electrode is welded to the tip endof the blade 1 to form a cBN-containing coating film 10. Here, onlysections of the blade 1 and discharge electrode 11 are shown, the blade1 is fixed by a blade fixing jig, and the discharge electrode 11 isfixed by an electrode fixing jig (not shown). It is to be noted thatFIG. 3 shows an example of the blade, but a labyrinth seal which is thesame rotating member can also be coated with the hard material in asimilar method. It is to be noted that in the-figure, reference numeral13 denotes the blade fixing jig.

In the above description, cBN is used as the hard material, and cBN is acoating material optimum for the turbine blade exposed at a hightemperature, in that Vickers hardness is 4500 HV at room temperature,and Vickers hardness close to 2000 HV can be maintained even at hightemperature of 900° C. or more. Additionally, from the viewpoint ofresistance to oxidation, a hard material of TiC, WC can be used in therotating member for use at a low temperature, Cr₃C2 can be used in therotating member for use at a high temperature, and ZrO₂—Y or Al₂O₃ canbe used in the rotating member for use at a further high temperature.Therefore, according to the present invention, a coating film containingTiC, WC, or cBN is formed on the rotating member for use at the lowtemperature, a coating film containing cBN or Cr₃C2 is used in therotating member for use at the high temperature, and a coating filmcontaining ZrO₂—Y or Al₂O₃ is formed on the rotating member for use atthe further high temperature. Needless to say, these hard materials mayalso be mixed to form an optimum coating film. It is to be noted that adischarge coating technique is disclosed, for example, in “SurfaceTreatment Method of Metal Material by In-liquid Discharge” of JapaneseLaid-Open Patent Publication No. 7-197275, and the description isomitted.

Here, since ceramics such as cBN are hard insulating materials, a singleceramic such as cBN cannot be formed into the discharge electrode, butthe discharge electrode containing the ceramics such as cBN can beformed by use of a conductive binder. For example, Co-based alloy powdercan be used as a binder, and ceramic powder such as cBN may be mixedwith a Co-based alloy powder, charged in a press mold, andcompressed/molded. It is to be noted that an amount of binder ispreferably about 50% or more by a volume ratio.

Furthermore, the powder of ceramics such as cBN may be coated withtitanium (Ti), nickel (Ni), or cobalt (Co) which is a binder to form thedischarge electrode. A particle diameter of the whole powder needs to besmaller than a pole distance between the electrode and a work during adischarge surface treatment, and is therefore preferably about 10 μm orless. The powder of ceramics such as cBN can easily be coated with athin coating film of a Ti, Ni, or Co metal by vapor deposition.

When the conductive binder is mixed, and the discharge electrodecontaining the ceramics such as cBN is formed in this manner, thedischarge can be caused in the portion of the binder, the dischargeelectrode is brought into a molten state by heat energy, and a part ofthe discharge electrode can be welded/attached to the tip end of therotating member such as the blade. As a result, the tip end of therotating member can be coated with a hard coating film containing theceramics such as cBN.

Here, Table 1 shows results of a wear test in which two test pieces(upper and lower test pieces) coated by the coating method of thepresent invention are ground (rubbed) with each other at the hightemperature. TABLE 1 Coating material Wear amount (μm) Upper test pieceNi alloy 600 or more Lower test piece cBN coating 0

The upper test piece is RENE77 which is a nickel-based alloy, and thelower test piece is cBN which is the coating film of the presentinvention. For test conditions, temperature: 800 degrees centigrade,surface pressure: 7 MPa, cycle number: 10⁷ cycles, and amplitude: 0.35mm. As seen from Table 1, a wear amount of 600 μm or more is measured onan Ni alloy, but no wear is detected on the coating film of cBN. Fromthis result, it is seen that cBN is superior in abrasive properties. Itis to be noted that this Ni alloy is an alloy constituted of a componentratio of Ni: 57%, Cr: 15%, Co: 15%, Mo: 5%, Ti: 3.5%, Al: 4.4, C: 0.1%.

When a so-called discharge coating method is used to coat the tip end ofthe rotating member such as the blade with the coating film containingthe ceramics such as cBN, the hard coat can easily be applied by use ofcharacteristics of the ceramics such as cBN, and a coating film havinggood adhesion and quality level can be coated as compared withconventional methods such as welding and thermal spraying. According tothe present invention, since a thin coating film (or a layer) that has athickness of several microns to 30 μm can be formed, the coating film isnot easily cracked, and precision can be controlled by a unit of severalμm. Therefore, it is possible to provide a coating method optimum forprecision components such as the blade and labyrinth seal.

Coarser surface roughness for abrasive properties of shaving theopponent component to be ground is preferable. In the example, thesurface roughness is coarser than 1.2 μmRa.

As described above, since the so-called discharge coating method is usedin the present invention, the pretreatments such as the masking andblast process are unnecessary, the coating film having good adhesion caneasily and inexpensively be formed, and further a coating filmcontaining ceramics such as cubic boron nitride (cBN) can be coated.Therefore, a portion of the rotating member requiring the abrasiveproperties can be coated with a hard coating film superior in abrasiveproperties.

A coating layer of the hard material is hard, and small in ductility.Therefore, a tensile stress applied to the component is not borne by amother material in a component having a large ductility, and is borneonly by the coating layer of the surface. Therefore, the surface cracks,and there is a possibility that the crack is developed into the mothermaterial. To avoid this, a method of imparting the ductility to thecoating layer is used.

Table 2 shows the number of cycles reaching destruction in a high cyclefatigue (HCF) test in which an outer diameter of a round rod is coatedwith the hard material and a tensile load is going to be repeated in anaxial direction.

Without any coating of the hard material, the material does not break upto one million cycles. However, in the coating in which a ratio of acoated area in a coating surface with the hard material, that is, acoverage (see FIG. 4) of coating is 98%, the material breaks at 20thousand cycles. When the coverage is suppressed at about 95%, thematerial does not break up to one million cycles. TABLE 2 Coating stateCycle number of break No coating One million cycles 98% coverage of TiC20 thousand cycles 95% coverage of TiC One million cyclesHFC test conditions: 500° C., 650 MPa, pull of round rod having adiameter of 5 mm in axial direction at 30 Hz

When the coverage of the coating is lowered to 95% or less, the abrasiveproperties of the whole coating surface are slightly sacrificed toincrease the ductility. When the coverage is raised, the ductilitydecreases, and fatigue strength drops. However, at 95%, the fatiguestrength does not largely drop, and the abrasive properties little drop.In one method of lowering the coverage, a discharge time is reduced, arange in which the discharge does not occur is left, and the coveragecan be reduced. The treatment is usually performed for a time of fiveminutes/square centimeter, but the time may be reduced to about 3.8minutes/square centimeter.

A calculation equation is as follows:Time for obtaining a coverage of 95%=time for obtaining a coverage of98%* LOG(1−0.95)/LOG(1−0.98).The coverage of 98% is regarded as a coverage of 100%. To calculate thetime from a time for obtaining a coverage of 50%, 0.98 in LOG(1−0.98) ischanged to 0.5.

In another method, as shown in FIG. 5, with the use of the electrode towhich a metal powder that is not easily carbonized is added, ductileproperties of the metal is imparted to the coating layer. When theelectrode contains 5% or more of a metal that is not easily carbonized,5% or more of a portion having the ductility remains, and an effectsimilar to that of Table 2 can be expected. Also in this method, theabrasive properties of the whole coating surface are slightlysacrificed. Examples of the metal which is not easily carbonized includecobalt, nickel, and iron. For the coverage, one blade has beendescribed. However, there are a large number of blades. Therefore, evenif the coverage is low, or the abrasive properties are not seen in acertain portion of a certain blade, the other blades can cover theproperties. This also applies to an annular seal because if one portionon the circumference of the annular seal has the abrasive properties, itis possible to obtain the abrasive properties.

Moreover, as still another method, as shown in FIG. 6, a porous layer isformed as a base for the coating layer of the hard material in order toprevent the crack of the coating layer from being developed into themother material. The porous layer is formed under the coating layer.This base is also formed by discharge coating. The porous layer having athickness of 0.05 mm or more can be formed by using the electrodeobtained by compression molding of a powder of metals such as Stellite.Thereafter, the porous layer is coated with the hard material.

Moreover, the surface of the coating of the hard material is peened, thesurface is accordingly stretched, a compression stress is left, and atensile stress is reduced even when the mother material is elongated.The fatigue strength can be enhanced by the effect.

FIGS. 7A to 7C, 8A to 8C, 9A and 9B are perspective views showing fifthto seventh embodiments of the rotating member of the present invention.It is to be noted that in these figures, a platform or a dovetail on adisk side is omitted.

In the turbine blade 1 of FIG. 7A, the corner of the blade in a rotationadvance direction, that is, the blade tip end of a blade surface on theback side and a tip end surface are coated with a coating 20 of the hardmaterial.

In a thin turbine blade of FIG. 7B, the blade tip end of a blade surfaceon the back side and the entire tip end surface are coated, and theopposite surface may not be coated.

In the turbine blade of FIG. 7C, the blade tip end of a blade surface onthe back side is coated, and the entire tip end surface is not coated.

In the turbine blade 2 with the chip shroud of FIG. 8A, the corner ofthe tip end of a chip fin 4 in the rotation advance direction, or thesurface of the chip fin 4 in the rotation advance direction, that is,the backside surface of the tip end of the chip fin 4 on are coated witha coating 21 of the hard material. It is to be noted that the chipshroud 3 is disposed to prevent resonance of the blades 2 at the time ofa high-speed rotation of the gas turbine and to prevent ahigh-temperature gas from leaking to the outside of the blades 2.

In a small blade of FIG. 8B, the entire surface of the tip end and thesurface of the rotation advance direction (i.e., on the backside surfaceof the tip end of the chip fin 4) are coated, and the opposite surfacemay not be coated.

In the turbine blade of FIG. 8C, the surface of the rotation advancedirection (i.e., the backside surface of the tip end) is coated, and thewhole surface of the tip end is not coated.

In the compressor blade 1 of FIG. 9A, the corner of the blade in therotation advance direction, that is, the blade tip end of a bladesurface on the front side and the tip end surface are coated with acoating 22 of the hard material.

In the compressor blade of FIG. 9B, the surface of the rotation advancedirection, that is, the blade tip end of a blade surface on the frontside is coated, and the entire surface of the tip end is not coated.

In the blades of FIGS. 9A and 9B, an abrasive property test was carriedout by simulation of an actual device, a difference was not recognizedin the property.

As described above, the coating of the hard material is applied so as toshave the abradable coating by the tip ends of the blades 1, 2 by takingadvantage of the hardness difference, at the time of driving the blades1, 2 to keep a minimum chip clearance. The abradable coating is appliedon the casing or the shroud. Moreover, this phenomenon starts by thecontact between the casing or the shroud and the corners of the blades1, 2 in the rotation advance direction, and ends when the casing or theshroud is shaved. That is, after the contact of the corner, anotherportion of the same blade hardly contacts with the casing or the shroud.In consideration of this fact, the coating of the hard material does nothave to be applied over the entire region of the blade tip end as in therelated art. As described in the present invention, it is sufficientthat only the range of the contact with the abradable coating, that is,only the corner of the rotation advance direction, or only the surfaceof the rotation advance direction is coated with the coatings 20, 21, 22of the hard material. When the range to be coated is optimized in thismanner, the range to be coated is narrowed, the yield of products isenhanced, the operation time can be shortened, the expensive coatingmaterial can be saved, and the cost can be reduced.

FIG. 10 is a diagram showing a fifth embodiment of the coating methodaccording to the present invention, and is a diagram showing the coatingmethod of the blades shown in FIGS. 7A to 7C. In the coating method ofthe present invention, the blade 1 and a discharge electrode 23 issubmerged in the processing tank 12 filled with the dielectric liquid(oil), the discharge electrode 23 is disposed in the vicinity of thecorner in the rotation advance direction of the blade 1, the dischargeis caused between them, and only the corner of the blade 1 in therotation advance direction is coated with the coating 20 of the hardmaterial.

The coating 20 of the hard material is formed to have a very thinthickness of 10 to 20 μm (exaggerated for ease of seeing in the figure).Therefore, after molding the blade 1 as usual, it is sufficient to applythe coating 20 of the hard material only to a range of contact with theopposite member, that is, only the corner of the rotation advancedirection or the surface of the rotation advance direction. Needless tosay, the corner of the blade 1 is shaved by the thickness of the coating20 of the hard material by machine processing, and a casting mold inconsideration of the thickness beforehand may be used to mold the blade1.

Moreover, in a case of a thin blade, the coating of the hard materialmay be formed entirely on the rotation advance direction surface and thetip end surface. However, the surface disposed opposite to the rotationadvance direction surface does not have to be coated.

It is to be noted that only the sections of the blade 1 and dischargeelectrode 23 are shown in FIG. 10.

In this coating method, the discharge electrode 23 shaped so as to coatonly the blade tip end of the blade surface on the back side and the tipend surface is preferably used so that only the corner of the blade 1 inthe rotation advance direction can be subjected to the dischargecoating. For example, the discharge electrode 23 has a substantiallyL-shaped section, and a shape curved along the back side of the blade.

The electrode may be processed beforehand into a product shape. However,alternatively, the electrode may be formed in accordance with theproduct shape by the discharge on the discharge condition on which theelectrode is easily consumed. As this condition, the electrode is set tohave a minus polarity, and the discharge is caused on comparativelysmall energy condition on which the pulse width is set to 1 μs or less,and the current value is 10 A or less. Then, the damage onto the productis suppressed, and the electrode can accord with the product shape.

When the coating film is formed, the electrode is assumed to have theminus polarity, and the discharge is caused on comparatively largeenergy condition on which the pulse width is about 2 to 10 μs, and thecurrent value is about 5 to 20 A.

It is to be noted that although not shown, with the turbine blade withthe chip shroud 2 shown in FIGS. 8A to 8C, such an electrode to coat thecorner of the chip fin 4 in the rotation advance direction may be used.

In the discharge coating, the discharge is caused on the surfacesdisposed opposite to each other by application of a voltage between theblade 1 and the discharge electrode 23 submerged in the dielectricliquid, the surface of the discharge electrode 23 is molten by thedischarge, and the molten element is attached on the surface of theblade 1 to form the alloy on the surface. A solidified coating materialis used for the discharge electrode 23.

Since the thickness of the coating can be controlled by the degree ofseveral micrometers, the discharge coating is a coating method optimumfor the precision components such as the blade 1. Moreover, a placewhere the discharge does not occur is not coated. Therefore, since theportion to be coated can locally be coated, the pretreatments such asthe masking are unnecessary. Since heat generation is small, the bladeis not thermally deformed, and the post-treatment is also unnecessary.

As described above, in the present invention, since the coating range ofthe hard material is optimized, the yield of products can be enhanced.Since the operation time can be shortened, and the coating material canbe saved, the cost can be reduced. Furthermore, since the so-calleddischarge coating is used, only the corner of the rotation advancedirection of the blade or the surface of the rotation advance directioncan easily and inexpensively can be coated with the hard material.

Moreover, even when all the blades assembled onto a rotor are not coatedwith the hard material, some of the blades are coated with the hardmaterial, and it is then possible to obtain the effect. This alsoapplies to the annular seal, as long as one or more portions on thecircumference may have the abrasive properties.

FIG. 11 is a schematic diagram of a labyrinth seal structure accordingto an eighth embodiment of the rotating member of the present invention,and FIG. 12 is a front view of a labyrinth seal of FIG. 11. FIG. 13 is aschematic diagram of a discharge processing machine according to theeighth embodiment of the coating method according to the presentinvention.

As shown in FIGS. 11 and 12, a labyrinth seal structure 31 according tothe embodiment of the present invention is used in the gas turbine of ajet engine, and inhibits a leak of a combustion gas between an enginestationary component 33 and an engine rotating component 35. Thelabyrinth seal structure 31 includes, as constituting elements, ahoneycomb-shaped stationary-side honeycomb seal component 37 integrallydisposed on the engine stationary component 33, and a rotating labyrinthseal component 39 disposed inside the stationary-side honeycomb sealcomponent 37 and capable of rotating integrally with the engine rotatingcomponent 35. It is to be noted that a stationary-side abradable sealcomponent whose inside is coated with the abradable coat may also beused instead of the stationary-side honeycomb seal component 37.

A concrete constitution of the rotating labyrinth seal component 39which is an important part of the embodiment of the present invention isas follows.

That is, an annular seal component main body 41 which is a main body ofthe rotating labyrinth seal component 39 is integrally disposed on theengine rotating component 35, and a plurality of annular seal fins 43are integrally formed on the outer peripheral surface of the sealcomponent main body 41. Tip edges of the respective seal fins 43 arecoated with coats 45 of the hard material. Furthermore, for each coat 45of the hard material, an electrode 47 for coating having consumability(see FIG. 13) is used, and a pulsed discharge is caused between theelectrode 47 for coating and the tip edge of the seal fin 43. Theconstituting material of the electrode 47 for coating or the reactant ofthe constituting material forms into the coating film containing thehard material on a plurality of treated portions in the tip edges of theseal fins 43 by the discharge energy, and accordingly a plurality of(four in the embodiment of the present invention) local coats 45 a ofthe hard material are applied at equal intervals.

Here, in the embodiment of the present invention, in general, “theelectrode for coating having the consumability” means a green compactelectrode (including a thermally treated green compact electrode)obtained by compression molding of a powdered metal (including a metalcompound), a mixed material of the powdered metal and a powderedceramic, or the powdered ceramic having conductivity. “The electrode forcoating having the consumability” may also mean a silicon electrodeformed of solid silicon. It is to be noted that the ceramic havingconductivity is subjected to the surface treatment for forming aconductive coating film on the ceramic powder, and molded bycompression, so that the conductivity is secured. Especially, examplesof the “powdered metal” include Ti, Co, and the like, and the examplesof the “powdered ceramic” include cBN, TiC, TiN, TiAlN, AlN, TiB₂, WC,Cr₃C₂, SiC, ZrC, VC, B₄C, Si₃N₄, ZrO₂—Y, Al₂O₃, and the like.

The examples of the material which reacts by the discharge energy toform the coating film containing the hard material include Ti, W, Cr,Zr, Si, V, Mo, Nb.

Furthermore, the electrode 47 for coating has a shape approximate tothat of the portion to be treated in the tip edges of the seal fins 43.

Next, a concrete constitution of a discharge processing machine 49 foruse in coating the coat 45 of the hard material, and a coating methodfor coating the coat 45 of the hard material will be described withreference to FIG. 13.

That is, in the discharge processing machine 49 according to theembodiment of the present invention, a bed 51 is used as a processingmachine base, and a table 53 is disposed on the bed 51. The table 53 canbe moved in X-axis directions (left and right directions in FIG. 13) bydriving an X-axis servo motor (not shown), and can be moved in Y-axisdirections (front and back directions of a sheet surface of FIG. 13) bydriving a Y-axis servo motor (not shown).

A processing tank 55 in which dielectric liquid L such as dielectric oilis disposed on the table 53, and a support plate 57 is disposed in theprocessing tank 55. A support tool 59 to which the seal component mainbody 41 is fixed is disposed on the support plate 57.

A processing head 61 is disposed via a column (not shown) above the bed51 (above in FIG. 13), and this processing head 61 can move in Z-axisdirections (upward and downward directions in FIG. 13) by driving aZ-axis servo motor. Moreover, an electrode hold member 63 for holdingthe electrode 47 for coating is disposed on the processing head 61.

It is to be noted that the electrode hold member 63 and the support tool59 are electrically connected to a power supply 65.

Therefore, the seal component main body 41 is fixed by the support tool59 in a state in which a portion of the tip edge of the seal fin 43 tobe treated in the peripheral direction is directed right upwards in theprocessing tank 55. Next, the table 53 is moved in the X-axis and Y-axisdirections (at least either one direction) by driving the X-axis andY-axis servo motors. Thereby, the position of the seal fin 43 isdetermined such that the portion of the tip end of the seal fin 43 to betreated faces the electrode 47 for coating.

Moreover, the electrode 47 for coating is moved integrally with theprocessing head 61 in the Z-axis direction by driving the Z-axis servomotor, while a pulsed voltage is generated between the electrode 47 forcoating and the portion of the tip end of the tip fin 43 to be treatedin the dielectric liquid L. Accordingly, the electrode material of theelectrode 47 for coating is locally diffused in and/or welded to theportion of the tip edge of the seal fin 43 to be treated by thedischarge energy, and the portion of the tip edge of one seal fin 43 tobe treated can locally be coated with a local coat 45 a of the hardmaterial.

Furthermore, when the table 53 is moved in the Y-axis directions bydriving the Y-axis servo motor, the position of another seal fin 43 isdetermined such that the portion of the tip fin of the seal fin 43 to betreated faces the electrode 47 for coating. Then, as described above,the electrode material of the electrode for coating 47 is locallydiffused in and/or welded to the portion of the tip edge of this sealfin 43 to be treated by the discharge energy, and the portion of the tipedge of the seal fin 43 to be treated is locally coated-with the localcoat 45 a of the hard material.

After locally coating the portion of the tip edge of a plurality of theseal fins 43 to be treated with the local coat 45 a of the hardmaterial, the similar operation is repeated. Thereby, also the otherportions of the tip edges of a plurality of the seal fins 43 to betreated are also locally coated with the local coats 45 a of the hardmaterial.

Next, the function of the embodiment of the present invention will bedescribed.

The rotating labyrinth seal component 39 includes the coat 45 of thehard material. Therefore, to integrally rotate the rotating labyrinthseal component 39 and the engine rotating component 35, even when theengine stationary component is deformed and the rotating labyrinth sealcomponent 39 contacts with the stationary-side honeycomb seal component37, the stationary-side honeycomb seal component 37 is only shaved bythe coat 45 of the hard material in the rotating labyrinth sealcomponent 39. The rotating labyrinth seal component 39 is substantiallyhardly shaved.

Accordingly, the clearance between the stationary-side honeycomb sealcomponent 37 and the rotating labyrinth seal component 39 is inhibitedfrom increasing during the rotation of the engine rotating component 35,and the seal effect of the labyrinth seal structure 31 can be kept in anappropriate state. The rotating labyrinth seal component 39 is setbeforehand so as to slightly contact with the stationary-side honeycombseal component 37 at the time of the initial rotation of the enginerotating component 35. Accordingly, the clearance between thestationary-side honeycomb seal component 37 and the rotating labyrinthseal component 39 can be set to be as small as possible during and afterthe initial rotation, and the seal effect of the labyrinth sealstructure 31 can further be enhanced.

Moreover, coating of the coats 45 of the hard material is performed onthe portions of the tip edges of the seal fins 43 by diffusing and/orwelding of the electrode material of the electrode 47 for coating by thedischarge energy generated between the electrode for coating 47 and theportion of the tip edge of the seal fin 43 without performing theplating or thermal spraying. Therefore, in the production of therotating labyrinth seal component 39, the coating post-treatments suchas the blast treatment and the process of removing the masking tape areunnecessary.

Furthermore, the boundary portion between the coat 45 of the hardmaterial formed by the discharge energy and the mother body of the sealfin 43 has alloy composition changing properties, and the coat of thehard material can firmly be connected to the tip edge of the seal fin43.

Moreover, the coat 45 of the hard material includes a plurality of localcoats 45 a of the hard material. In other words, the electrode material47 of the electrode for coating is locally diffused in and/or welded toa plurality of portions to be treated of the peripheral direction in thetip edge of the-seal fin 43, not in the whole periphery of the tip edgeof the seal fin 43. Therefore, the electrode 47 for coating can beformed to have a small and simple shape in accordance with the sizeand/or the shape of the portion of the tip edge of the seal fin 43 to betreated. Accordingly, the amount of the electrode material used to formthe electrode 47 for coating can be reduced.

It is to be noted that as described above, the coat 45 of the hardmaterial (local coat 45 a of the hard material) can firmly be connectedto the tip edge of the seal fin 43. Therefore, even when the entire tipedge periphery of the seal-fin 43 is not coated with the coat 45 of thehard material, the sufficient abrasive properties of the entire rotatinglabyrinth seal component 39 can be achieved by a plurality of localcoats 45 a of the hard material.

As described above, according to the embodiment of the presentinvention, in the production of the rotating labyrinth seal component39, the coating pretreatments such as the blast process and the processof attaching the masking tape, and the coating post-treatments such asthe process of removing the masking tape are not required. Therefore,the operation time required for the production of the rotating labyrinthseal component 39 is reduced, and it is easy to enhance the productivityof the rotating labyrinth seal components 39.

Moreover, since the coat 45 of the hard material can firmly be connectedto the tip edge of the seal fin 43, the coat 45 of the hard materialdoes-not easily peel off from the tip edge of the seal fin 43, and thequality level of the rotating labyrinth seal component 39 is stabilized.

Furthermore, the entire rotating labyrinth seal component 39 hassufficient abrasive properties, and the electrode 47 for coating can beformed to have the small and simple shape in accordance with thesize/shape of the portion to be treated of the tip edge in the seal fin43. Moreover, the amount of the electrode material used to form theelectrode for coating 47 can be reduced. Therefore, the production costof the rotating labyrinth seal component 39 can be reduced.

It is to be noted that the present invention is not limited to thedescription of the embodiment of the present invention. For example,instead of the discharge in the dielectric liquid L, the discharge inthe electrically insulating gas can be performed. Thus, variousmodifications can be carried out.

As described above, according to the present invention, in theproduction of the rotating labyrinth seal component, the coatingpretreatments such as the blast process and the process of attaching themasking tape, and the coating post-treatments such as the process ofremoving the masking tape are not required. Therefore, the operationtime required for the production of the rotating labyrinth sealcomponent is reduced, and it is easy to enhance the productivity of therotating labyrinth seal components.

Moreover, since the coat-of the hard material can firmly be connected tothe tip edge of the seal fin, the coat of the hard material does noteasily peel off from the tip edge of the seal fin, and the quality levelof the labyrinth seal is stabilized.

Furthermore, in addition to the above-described effect, the entirerotating labyrinth seal component has sufficient abrasive properties,and the electrode for coating can be formed to have the small and simpleshape in accordance with the size/shape of the portion to be treated ofthe tip edge in the seal fin. Moreover, the amount of the electrodematerial used to form the electrode for coating can be reduced.Therefore, the production cost of the rotating labyrinth seal componentcan be reduced.

It is to be noted that some preferable embodiments of the presentinvention have been described, but it would be understood that the scopeof the present invention is not limited to these embodiments.Conversely, the scope of the present invention includes allimprovements, modifications, and equivalents included in the appendedclaims.

1. A method for coating a rotating member, comprising the steps of:generating a pulsed discharge between a rotating member formed into apredetermined shape and a discharge electrode of a green compact indielectric liquid or gas to transfer a hard material of the dischargeelectrode or a hard material changed from a material of the dischargeelectrode onto the rotating member by each discharge pulse so that ahard concavity and convexity is formed on the rotating member, whereinthe green compact includes the hard material or the material changinginto the hard material by the discharge; and repeatedly generating thedischarge pulse to form on the rotating member a hard coating filmhaving the concavity and convexity.
 2. The method for coating therotating member according to claim 1, wherein the hard coating film isan abrasive coating film that is formed on a part of the rotating memberand rubs against and shaves an opponent component.
 3. The method forcoating the rotating member according to claim 1, comprising the stepsof: generating discharge between the rotating member and the dischargeelectrode on a first discharge condition on which the dischargeelectrode is consumed so that a shape of the discharge electrode is madeto conform to a shape of a coating film forming portion on the rotatingmember; and thereafter generating discharge between the dischargeelectrode and the rotating member on a second discharge condition toform the coating film on the rotating member.
 4. The method for coatingthe rotating member according to claim 3, wherein on the first dischargecondition, the discharge electrode has a minus polarity, a pulse widthis 1 μs or less, and a current value is 10 A or less, and on the seconddischarge condition, the discharge electrode has a minus polarity, thepulse width is 2 to 10 μs, and a current value is 5 to 20 A.
 5. Themethod for coating the rotating member according to claim 1, wherein forthe coating film, a coverage which is a ratio of a coated area in acoating film forming portion is 95% or less.
 6. The method for coatingthe rotating member according to claim 1, wherein the coating film isformed by using the discharge electrode that contains 5% or more byvolume of a metal which does not easily react into carbide.
 7. Themethod for coating the rotating member according to claim 1, wherein atthe time of forming the coating film, a porous coating film is formed asa base, and then, the coating film including the hard material is formedon the porous coating film.
 8. The method for coating the rotatingmember according to claim 1, wherein the coating film is formed by usingthe discharge electrode of the green compact including one of or amixture of cBN, TiC, TiN, TiAlN, TiB₂, WC, Cr₃C₂, SiC, ZrC, VC, B₄C,Si₃N₄, ZrO₂—Y, and Al₂O₃.
 9. The method for coating the rotating memberaccording to claim 1, further comprising the step of peening the coatingfilm.
 10. A rotating member having an abrasive coating film on a partthereof that is formed by a pulsed discharge between the rotating memberand a discharge electrode of a green compact or solid silicon indielectric liquid or gas, wherein the green compact includes a hardmaterial or a material that changes into a hard material by thedischarge, and the abrasive coating film includes the hard material ofthe green compact or the hard material that is changed from the materialof the green compact or solid silicon by the discharge.
 11. The rotatingmember according to claim 10, wherein a coverage of coating is 95% orless in a coating film forming portion.
 12. The rotating memberaccording to claim 10, wherein the discharge electrode of the greencompact includes the hard material or the material that changes into thehard material by the discharge and includes 5% or more by volume of ametal which does not easily react into carbide.
 13. The rotating memberaccording to claim 10, wherein the coating film includes: a first porouslayer that is formed on the part of the rotating member by a pulseddischarge between the rotating member and a discharge electrode of agreen compact or solid silicon in dielectric liquid or gas, wherein thefirst porous layer includes a hard material of the green compact or ahard material that is changed from a material of the green compact orsolid silicon by the discharge; and a second layer that is formed on thefirst porous layer by a pulsed discharge between the first porous layerand a discharge electrode of a green compact or solid silicon indielectric liquid or gas, wherein the second layer includes a hardmaterial of the green compact or a hard material that is changed from amaterial of the green compact or solid silicon by the discharge.
 14. Therotating member according to claim 10, wherein the coating film includesa peened layer that is formed by penning the formed coating film. 15.The rotating member according to claim 10, wherein the dischargeelectrode includes the green compact, the thermally treated greencompact or solid silicon, the green compact is obtained by compressionmolding of a powdered metal, a powder of a compound of the metal, apowder of a ceramic or a mixture thereof, and the ceramic is one of or amixture of cBN, Cr₃C₂, TiC, TiN, TiAlN, TiB₂, ZrO₂—Y, ZrC, VC, B₄C, WC,SiC, Si₃N₄, and Al₂O₃.
 16. (Cancelled)
 17. The rotating member accordingto claim 10, wherein the coating film is formed on at least a portion ofthe part on the rotating member that faces or contacts with an opponentcomponent.
 18. The rotating member according to claim 10, comprising arotating member body and a casing component that covers the rotatingmember body, wherein the coating film having hard concavity andconvexity is formed on a part of the rotating member body by repeatedlygenerating discharge pulse between the rotating member body and thedischarge electrode to transfer the hard material of the dischargeelectrode or the hard material changed from the material of thedischarge electrode onto the part of the rotating member body, and thecasing component is made of a material of which hardness is smaller thanthat of the hard material of the coating film.
 19. The rotating memberaccording to claim 10, wherein the rotating member is a blade, the bladeand a discharge electrode are submerged in dielectric liquid or gas todispose the discharge electrode in the vicinity of a corner of a bladetip end in a rotation advance direction and/or the vicinity of a surfaceof the blade tip end in the rotation advance direction and/or thevicinity of the blade tip end surface, the discharge is generatedbetween the blade and the discharge electrode so that the coatingincluding the hard material is formed on the corner of the blade tip endin the rotation advance direction, or the adjacent surface to the bladetip in the rotation advance direction, or the end surface of the bladetip, or both of the adjacent surface to the blade tip in the rotationadvance direction and the end surface of the blade tip.
 20. The rotatingmember according to claim 10, wherein the abrasive coating filmincluding the hard material is formed on not all, but some of blades ofa rotor or a blisk.
 21. The rotating member according to claim 10,wherein the rotating member is a rotating labyrinth seal component whichis one of structure elements of a labyrinth seal structure to suppress aleak of a gas or liquid between a stationary component and a rotatingcomponent, the rotating member comprises: an annular seal component mainbody; and an annular seal fin integrally formed on an outer peripheralsurface of the seal component main body, a tip edge of the seal fin iscoated with the abrasive coating film including the hard material, thedischarge electrode having consumability is used, a pulsed discharge isgenerated between the discharge electrode and the tip edge of the sealfin in dielectric liquid or gas so that the abrasive coating film isformed to include the hard material of the discharge electrode or thehard material changed from the material of the discharge electrode bythe discharge.
 22. The rotating member according to claim 21, whereinthe abrasive coating film including the hard material comprises aplurality of local coating films locally formed on a plurality ofportions in a peripheral direction in the tip edge of the seal fin. 23.A labyrinth seal structure which suppresses a leakage of a gas or liquidbetween a stationary component and a rotating component, comprising: astationary-side seal component integrally disposed on the stationarycomponent; an annular seal component main body which is disposed insidethe stationary-side seal component and which is capable of rotatingintegrally with the rotating component and which is integrally disposedon the rotating component; an annular seal fin integrally formed on anouter peripheral surface of the seal component main body; and a hardcoat formed on the tip edge of the seal fin, wherein the hard coat is acoating film including a hard material constituted of a constitutingmaterial or a reactant of the constituting material of an electrode forcoating formed on the tip edge of the seal fin by a discharge energy ofa pulsed discharge between the electrode for coating and the tip edge ofthe seal fin, and the electrode for coating has consumability.
 24. Thelabyrinth seal structure according to claim 23, wherein the coatincluding the hard material comprises a plurality of local coating filmslocally formed on a plurality of portions in a peripheral direction inthe tip edge of the seal fin.
 25. A method for manufacturing a rotatingmember of a blade or a labyrinth member, comprising: a first step offorming a forging material or a casting material into a predeterminedshape by mechanical processing; and a second step of generating a pulseddischarge between a rotating member formed into a predetermined shapeand a discharge electrode of a green compact or solid silicon indielectric liquid or gas to transfer a hard material of the dischargeelectrode or the hard material changed from a material of the dischargeelectrode onto the rotating member by each discharge pulse so that ahard concavity and convexity is formed on the rotating member, whereinthe green compact includes the hard material or the material changinginto the hard material by the discharge, and repeatedly generating thedischarge pulse to form on the rotating member a hard coating filmhaving the concavity and convexity.
 26. The method for manufacturing therotating member according to claim 25, wherein in the second step, anabrasive coating film that rubs against and shaves an opponent componentis formed as the hard coating film on a part of the rotating member. 27.The method for manufacturing the rotating member according to claim 25,wherein the second step comprises the steps of: generating dischargebetween the rotating member and the discharge electrode on a firstdischarge condition on which the discharge electrode is consumed so thata shape of the discharge electrode is made to conform to a shape of acoating film forming portion on the rotating member; and thereaftergenerating discharge between the discharge electrode and the rotatingmember on a second discharge condition to form the coating film on therotating member.
 28. The method for manufacturing the rotating memberaccording to claim 27, wherein on the first discharge condition, thedischarge electrode has a minus polarity, a pulse width is 1 μs or less,and a current value is 10 A or less, and on the second dischargecondition, the discharge electrode has a minus polarity, the pulse widthis 2 to 10 μs, and a current value is 5 to 20 A.
 29. The method formanufacturing the rotating member according to any one of claim 25,wherein during the forming of the coating film in the second step, adischarge condition is controlled to set a coverage to be 95% or less inthe coating film forming portion, the coverage being a ratio of an areaat which the coating film including the hard material is formed.
 30. Themethod for manufacturing the rotating member according to claim 29,wherein the ratio of the coverage is controlled by reducing a dischargetreatment time to 76% or less of a discharge treatment time for acoverage of 100%.
 31. The method for manufacturing the rotating memberaccording to claim 25, wherein in the second step, the green compactelectrode containing 5% or more by volume of a metal which does noteasily react into carbide is used to perform the discharge.
 32. Themethod for manufacturing the rotating member according to claim 25,wherein the second step comprises the steps of: forming a porous coatingfilm on a coating film forming portion of the rotating member; andthereafter forming the coating film including the hard material on theporous coating film.
 33. The method for manufacturing the rotatingmember according to claim 25, wherein the discharge electrode of thegreen compact used in the second step is a green compact dischargeelectrode formed by compression molding of one of or a mixture of cBN,TiC, TiN, TiAlN, TiB₂, WC, Cr₃C₂, SiC, ZrC, VC, B₄C, Si₃N₄, ZrO₂—Y, andAl₂O₃.
 34. The method for manufacturing the rotating member according toclaim 25, further comprising: a third step of subjecting the coatingfilm formed in the second step to a peening treatment.